The invention is directed to a device for damping vibrations of a bridge having a bridge deck. The device comprises at least one damping wing arranged along at least one side of the bridge deck. The at least one damping wing dampens vibrations of the bridge, wherein the longitudinal direction of the at least one damping wing is arranged parallel to the longitudinal direction of the bridge deck.
It is desired to build suspension bridges with large span lengths. For example the Akashi Kaikyo bridge built during the late 1990's in Japan has a span length of nearly 2000 meters. Such large bridge lengths lead to considerable issues with regard to vibrations. This includes in particular wind induced vibrations and flutter. During fluttering of bridges, torsional vibrations and bending vibrations occur. They are usually self induced vibrations in which the dynamic wind forces are induced by the vibrations of the bridge deck. Flutter is caused in particular by wind speeds that are constant over time, contrary to gusts of wind or the like. If the wind speed acting on the bridge exceeds a critical value, the structural damping of the bridge deck is overcome by negative aerodynamic damping. At a further increase of the wind speed a system with a negative total damping can occur in which a small initial deformation can lead to an increasing vibration with practically unlimited amplitude and thus failure of the bridge. The characteristic structural value for flutter stability of bridges is the critical wind speed Ucr. It is a known fact that Ucr decreases with decreasing natural frequency of vibration and damping of the bridge. In particular bridges with large span lengths have low natural frequencies so that they are particularly prone to flutter.
From WO 2006/050802, a device for damping vibrations in particular in a bridge is known which comprises at least one aerodynamic control surface which is mounted in a rotational and/or displaceable manner and at least one mechanical damper which comprises a spring element. At least one constrained kinematic coupling is arranged between the mechanical damper and the aerodynamic control surface. Upon wind acting on the bridge the aerodynamic control surface is vibrating such that undesired vibrations of the bridge are dampened.
The known device has the advantage of being a passive system and, therefore, being highly reliable. However, it has moveable parts which make the implementation into a civil engineering structure an unusual task and possibly costly. It could also be argued that, even if more reliable than an active damper, it is in some ways less reliable because of moving parts that could fail.
Further, from EP 0 233 528 A2, a structure is known with fixed wings positioned with a vertical offset relative to the bridge deck. The wings are mounted on the hangers of a suspension bridge and, therefore, placed right above the edges of the bridge deck. While this known device has the advantage of no moveable parts and thus is particularly robust and reliable, it does not satisfactorily dampen vibrations of the bridge in practice.
Starting from the prior art described above it is the object of the invention to provide a device for damping vibrations of a bridge which is of robust and reliable construction and at the same time highly efficient with regard to damping of vibrations of a bridge.
The invention solves this object with a device according to claim 1. Advantageous embodiments can be found in the dependent claims, the specification and the drawings.